What can I see from the night sky with 8x21 binocular?

Well, ..., honestly 8x21's are pretty underpowered for astronomy. However, you could always look at the moon. The planets Mercury, Venus. BTW, be-careful to NEVER point your binoculars at the Sun or at planets when they are close to the sun. Mars, Jupiter, Moons of Jupiter, Saturn, and possibly Uranus. You could also see Bright Comets, and some of the brightest Messier objects like The Orion Nebula and Andromeda Galaxy.

If yo have a chance, though you may want to upgrade to 12x50 binoculars. Wal*Mart sells the Bushnell Powerview 12x50 binoculars for $34.95 and they are an excellent pair of binoculars. Also now is a good time for you to connect with your local astronomy club. They can certainly help you with your passion for astronomy.

I'd agree with the other responders to your question (thus far :)) 8X21 binoculars won't allow you to see much. From the article Astronomy Binoculars on Binoculars.com:

"Choose by Objective Lens - Not by Magnification

When selecting your astronomy binocular, choose by the objective lens size your willing to use. The magnification levels usually scales with the size of the objective lenses. Some very common sizes for astronomy binoculars are 10x50, 12x60, 15x70, 20x80 and 25x100. There may be some slight changes to these among the many binoculars, but this is a good guide to use. The more objective lens you have, the more light-gathering power your binocular will have, allowing for greater amounts of magnifications. "

Not very much. The minimum recommended sizes for astronomical binoculars are 7x50 and 10x50. An 8x21 has too small an aperture to be of much use on anything other than the Moon.

The only binoculars I have are 7x20, so welcome to my club. It's not much, but still a good tool for star-hopping and finding some interesting objects. You can see the Pleiades, the Hyades, the Alpha Persei cluster, the Andromeda galaxy, the Orion Nebula, and lovely star fields in Cygnus.

http://en.wikipedia.org/wiki/Pleiades_(star_cluste...

http://en.wikipedia.org/wiki/Hyades_(star_cluster)

http://en.wikipedia.org/wiki/Alpha_Persei

http://en.wikipedia.org/wiki/Andromeda_Galaxy

http://en.wikipedia.org/wiki/Orion_nebula

http://en.wikipedia.org/wiki/Cygnus_(constellation...

Clear skies!